Alpha induced reaction cross section measurements on ¹⁶²Er for the astrophysical γ process

The cross sections of the ¹⁶²Er(α,γ)¹⁶⁶Yb and ¹⁶²Er(α,n)¹⁶⁵Yb reactions have been measured for the first time. The radiative alpha capture reaction cross section was measured from E_c.m.=16.09 MeV down to E_c.m.=11.21 MeV, close to the astrophysically relevant region (which lies between 7.8 and 11.48 MeV at 3 GK stellar temperature). The ¹⁶²Er(α,n)¹⁶⁵Yb reaction was studied above the reaction threshold between E_c.m.=12.19 and 16.09 MeV. The fact that the ¹⁶²Er(α,γ)¹⁶⁶Yb cross sections were measured below the (α,n) threshold at first time in this mass region opens the opportunity to study directly the α-widths required for the determination of astrophysical reaction rates. The data clearly show that compound nucleus formation in this reaction proceeds differently than previously predicted